1. Field of the Invention
The present invention is generally directed to electrostatic chucks for use in semiconductor fabrication to hold semiconductor wafers in place for processing operations. Particularly, the present invention is directed to electrostatic chucks having tailored electrical resistivity properties and/or tailored compositions for improved performance, as well as methods for processing semiconductor wafers using such an electrostatic chuck.
2. Description of the Related Art
Electrostatic chucks, also know as susceptors, are employed to support substrates such as semiconductor (silicon) wafers during the manufacture of semiconductor devices. Electrostatic chucks are generally fabricated from ceramic materials, including aluminum nitride (AlN), which has a number of desirable properties. Such properties include desirable shock resistance, thermal conductivity, thermal expansion properties, and erosion and corrosion resistance in the semiconductor fabrication environment, which many times includes a corrosive plasma.
While various types of electrostatic chucks have been utilized in semiconductor fabrication, Coulombic and Johnson-Rahbek electrostatic chucks have been primarily used. Typically, Johnson-Rahbek electrostatic chucks have a dielectric ceramic body which has an electrical resistivity of 108 to about 1013 ohm-cm, such as 109 to about 1011 ohm-cm at working temperature. Working temperature may vary, such as room temperature for dry etching processing, and about 250° C. to about 700° C. for deposition processes (including PVD and CVD).
Various techniques have been employed in the art for reducing the intrinsic resistivity of pure aluminum nitride, which tends to be too high for efficient electrostatic chuck operation, such as on the order of 1013 ohm-cm. Such techniques include use of resistivity modifying agents to reduce the resistivity of the electrostatic chuck. While attempts at reducing the resistivity of aluminum nitride-based electrostatic chucks have been successful, it has been recognized that such low resistivities may undesirably result in leakage current, in which current flows away from the chucking surface supporting the semiconductor wafer. Such leakage current undesirably affects the chucking and de-chucking efficiency and performance. Accordingly, the art has sought to develop electrostatic chucks having reduced leakage current and improved chucking and de-chucking performance through the operational life of the electrostatic chuck.